1. Field of the Invention
The present invention relates to an electric junction box used in mutual connection of wire harnesses and the like.
2. Description of the Prior Art
An electric junction box used in mutual connection of wire harnesses generally has a construction such as shown in FIG. 9. In the figure, reference numeral 1 represents an upper case and 2 a lower case, the upper and lower cases 1 and 2 accommodating therebetween a plurality of busbar conductors 3A, 3B . . . stacked one on the other. Each busbar conductor consists of an insulating substrate 6 and a plurality of busbars 4 having desired patterns arranged on one or both surfaces of the substrate. Each busbar 4 is integrally formed with a plurality of upwardly or downwardly projecting tabs 5 adapted to pass through tab insertion holes 7 in insulating substrates 6 and project outside the upper or lower case 1, 2, whereat the tabs 5 are introduced into connectors such as connector insertion portions 11, fuse connectors 12 and relay connectors 13 to be connected to terminal parts of wire harnesses such as connectors 14, fuses 15 and relays 16 with or without the aid of male-female relay terminals 10. Designated 8 in the figure is a busbar-accommodating groove defined by opposing ribs 8a, 8a. Each busbar 4 is arranged in a groove 8 and prevented from inadvertent disengagement therefrom by having a weld boss 9 hot pressed with a jig (not shown).
Busbars 4 that form internal circuits of an electric junction box are conventionally formed by being punched out from the same conductive metal plate for each layer, thus rendering it difficult to introduce a change only to part of the busbars. As a result, in case motor vehicles of the same model, for example, are produced with several grades according to presence or non-presence of optional circuits, it is conventional practice that the busbars in one layer are of such combination as to provide a maximum capacity that suits the vehicles of the highest grade, resulting in some of the busbars remaining unused depending on the vehicle grade. Further, busbars (and busbar conductors) for use in vehicles of ore model are not usable in vehicles of another model due to differences in circuits, thus necessitating a fresh start in designing circuit-forming busbars and producing punching dies, which is very costly.